Holographic shrink wrap element and method for manufacture thereof

ABSTRACT

A holographic shrink wrap element containing a shrink wrap film and a layer on the shrink wrap film, wherein the layer contains a holographic image. A process for preparing a holographic shrink wrap element includes providing, in the following order, a holographic polymer film having a holographic surface, a layer on the holographic surface and a shrink wrap film, and removing the holographic polymer film, leaving the holographic image on the layer.

FIELD OF THE INVENTION

The present invention is a holographic shrink wrap element containing ashrink wrap film (also known as “heat shrink film” or “shrink film”) anda layer containing a holographic image and a process for the preparationthereof. Applications for such elements include compact disc (CD)package overwraps, bottle wraps such as aluminum beverage can coveringsand package labels (especially food packaging). An additionalapplication of the invention is use of the holographic shrink wrapelement for sealing bands used in tamper evident applications.

BACKGROUND OF THE INVENTION

Shrink wrap films have seen a wide variety of applications such as CDoverwraps, bottle wraps, beverage container wrappings, labels forpackaging, especially food packaging, and sealing bands used in tamperevident applications. In an increasingly competitive marketplace, shrinkwrap films are being called upon to provide more functionality includingpackaging design and security, primarily due to the difficulty inforging holograms. Heretofore, shrink wrap films have not been availablewith holographic patterns which are able to provide strong eye appealand security simultaneously.

For example, materials are typically rendered holographic viamicroembossing at elevated temperatures and pressures. As set forth inU.S. Pat. Nos. 4,913,858; 5,164,227; 5,503,792; 5,155,604; and5,662,986; substrates are rendered holographic under high heat andpressure. Because shrink wrap films are engineered to shrink under heat,it is not possible to emboss such films using traditional techniques.

Further, it is known that films can be imparted with a microembossedstructure during an extrusion process. For example, U.S. Pat. No.5,003,915 teaches the method of creating a holographic image on sheetmaterial via a casting process while U.S. Pat. Nos. 4,913,858;5,164,227; and 5,155,604 teach an extrusion onto a paper substrate priorto hot embossing. Extrusion of shrink wrap film onto an embossing chillroller is further discussed in U.S. Pat. No. 5,182,069. Thedisadvantages of such routes include the need for capital equipment suchas extruders and, in the latter case, the depth of embossing (up to twoorders of magnitude deeper) which can be better described asmacroembossing.

Rendering materials holographic via a transfer process is taught in U.S.Pat. Nos. 5,383,687 and 5,662,996. Both inventions therein utilize heatand pressure to achieve their ends and focus on aluminum metallizedtransfers. U.S. Pat. No. 5,383,687 describes hot stamping holographicfoil onto sheets while U.S. Pat. No. 5,662,986 transfers a holographicimage to a paper substrate under elevated temperatures and pressures. Inboth inventions, the heat required is well beyond the temperatures atwhich the shrink wrap film will begin to contract, rendering suchapproaches in the context of shrink wrap films inappropriate.

Heretofore, the art provides no means for producing holographic heatshrink elements wherein heat shrink film can be rendered holographicwith the use of common coating/laminating equipment.

SUMMARY OF THE INVENTION

The present invention provides a holographic shrink wrap elementcontaining a shrink wrap film and a layer containing a holographicimage. The present invention is also directed to a process for thepreparation thereof. The process of the present invention allows for themanufacture of full or selectively holographic web areas with clear,reflective, or high index coatings while imparting abrasion resistanceand a high level of printability without activating the film's shrinkqualities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a holographic shrink wrap element ofthis invention containing a holographic polymer film 1/adhesive 2/shrinkwrap film 3 prior to stripping the holographic polymer film. Theadhesive shown in this figure can be either an electron beam coating ora cold laminating adhesive.

FIG. 2 is a cross sectional view of the holographic shrink wrap elementof this invention containing a holographic polymer film 1/adhesive 2(e.g., electron beam coating or cold laminating adhesive)/shrink wrapfilm 3, wherein the holographic polymer film 1 is being removed, leavingthe holographic image on the surface of the adhesive 2.

FIG. 3 is a cross sectional view of the holographic shrink wrap elementof this invention containing a holographic polymer film 1/imageintensifying layer 4/adhesive 2 (e.g., electron beam coating or coldlaminating adhesive)/shrink wrap film 3, wherein the holographic polymerfilm 1 is being removed, leaving the holographic image on the surface ofthe image intensifying layer 4.

FIG. 4 is a cross sectional view of the holographic shrink wrap elementof this invention containing a holographic polymer film 1/releasecoating 5/image intensifying layer 4/adhesive 2 (e.g., electron beamcoating or cold laminating adhesive)/shrink wrap film 3, wherein theholographic polymer film 1 is being removed, leaving the holographicimage on the surface of the release coating.

FIG. 5 is a cross sectional view of the holographic shrink wrap elementof this invention containing a holographic polymer film 1/releasecoating 5/image intensifying layer 4/tie coat 6/adhesive 2 (e.g.,electron beam coating or cold laminating adhesive)/shrink wrap film 3,wherein the holographic polymer film is being removed, leaving theholographic image on the surface of the release coating.

FIG. 6 is a schematic of an image transfer process which can be utilizedin preparing the holographic shrink wrap element illustrated in FIG. 1wherein the adhesive is an electron beam curable coating.

FIG. 7 is a schematic of another image transfer process which can beutilized in preparing the holographic shrink wrap element of thisinvention.

DETAILED DESCRIPTION OF THE INVENTION

In a first embodiment (first embodiment), the holographic shrink wrapelement of the present invention contains a shrink wrap film and a layercontaining a holographic image. The layer containing the holographicimage may be, where appropriate, an adhesive, an image intensifyinglayer or a release coating.

More specifically, in a second embodiment of the present invention(second embodiment), the holographic shrink wrap element contains ashrink wrap film and an adhesive, wherein the adhesive contains aholographic image.

In a third embodiment of the invention (third embodiment), theholographic shrink wrap element contains, in the following order, ashrink wrap film, an adhesive, and an image intensifying layer, whereinthe image intensifying layer contains a holographic image.

In a fourth embodiment of the invention (fourth embodiment), theholographic shrink wrap element contains, in the following order, ashrink wrap film, an adhesive, and a release coating, wherein therelease coating contains a holographic image.

The second, third and fourth embodiments are more specific embodimentsof the first embodiment.

The shrink wrap film used in this invention is generally a commerciallyavailable non-holographic shrink wrap film such as REYNOLON® 5044 fromReynolds Shrink Films, DuPont CLYSAR® shrink film or GLS grade(polyolefin manufactured by UCB). Such films are typically high-claritypolyolefins or copolymers thereof. Typical thicknesses range from 12.5to 38 micron with a percent shrinkage between five and 70% butpreferably between seven and 15%. Of these, the preferred shrink wrapfilm is GLS grade from UCB.

The adhesive which may typically be used in this invention includes anelectron beam coating or a cold laminating adhesive. Such coatings areadvantageous because they effect lamination and transfer without theapplication of heat. Typical electron beam curing coatings which may beused in the invention include ethylenically unsaturated monomers andoligomers such as acrylates. These may include, but are not limited to,urethane acrylates, polyester acrylates, and epoxy acrylates withsingle, double or multiple functionality. The cold laminating adhesiveswhich may be used in this invention are typically pressure sensitive.These may be of either solvent or water-based chemistry and include, butare not limited to, acrylics, one or two part urethanes, polyesters, orrubber. Morton International manufactures a wide range of coldlaminating adhesives such as MORSTIK® 227 (water-based pressuresensitive adhesive). Typical coating weights for the adhesive are in therange of 4-5 g/m².

The image intensifying layer may be any reflective or high indexmaterial. For example, the image intensifying layer may be at least oneof the following: a vacuum vapor deposited aluminum; silicon monoxide;silicon dioxide; aluminum oxide; magnesium fluoride; zinc sulfide;titanium dioxide; tin tungsten oxide and indium tin oxide. Of these, thevacuum vapor deposited aluminum is preferred. Typical coatingthicknesses for the image intensifying layer are 200-400 Å. The imageintensifying layer is optionally present with the release coating.

Typical components for the release coating are the following: threeparts methyl methacrylate polymer: one part nitrocellulose;, one partmethyl methacrylate polymer: one part nitrocellulose; nitrocellulose;methyl methacrylate polymer; cellulose acetate; saturated vinylacetate/vinyl chloride terpolymer such as VYNS-3 (Union Carbide); or anamorphous saturated linear polyester such as DYNAPOL® S-1606 (apolyester made by H{umlaut over (u)}ls). Of these, the saturated vinylacetate/vinyl chloride terpolymer and amorphous saturated linearpolyester are preferred. Typical coating weight for the release coatingis between 30-40 mg/m².

If desired, a tie coat can be provided between the release coating andthe adhesive or between the image intensifying layer and the adhesive. Apreferred tie coat is a vinyl chloride/vinyl acetate terpolymer. Typicalcoating weight for the tie coat is between 30-40 mg/m².

Colorants and other conventional additives may be added whereappropriate. For example, colorants which will not interfere with theelectron beam curing process may be added to the release coating toimpart color to the finished shrink wrap element. At 1-5% on a solidsbasis, organic or inorganic pigments such as iron oxides will provide alight color to the coating without absorbing electron beam energy. Whena cold laminating adhesive is employed, slightly higher concentrationsof colorant may be added.

The present invention also includes a process for preparing theholographic shrink wrap element of the invention. For example, a processfor preparing the first embodiment of the invention comprises providing,in the following order, a holographic polymer film having a holographicsurface, a layer on the holographic surface and a shrink wrap film, andremoving the holographic polymer film, leaving the holographic image onthe layer.

A process for preparing the second embodiment of the invention comprisesproviding, in the following order, a holographic polymer film having aholographic surface, an adhesive on the holographic surface and a shrinkwrap film, and removing the holographic polymer film, leaving theholographic image on the adhesive.

A process for preparing the third embodiment of the invention comprisesproviding, in the following order, a holographic polymer film having aholographic surface, an image intensifying layer on the holographicsurface, an adhesive and a shrink wrap film, and removing theholographic polymer film, leaving the holographic image on the imageintensifying layer. If desired, the third embodiment may furthercomprise providing the tie coat between the image intensifying layer andthe adhesive

A process for preparing the fourth embodiment of the invention comprisesproviding, in the following order, a holographic polymer film having aholographic surface, a release coating on the holographic surface, anadhesive and a shrink wrap film, and removing the holographic polymerfilm, leaving the holographic image on the release coating. If desired,the fourth embodiment may further comprise providing the imageintensifying layer between the release coating and the adhesive or thetie coat between the release coating and the adhesive. Also, if desired,the fourth embodiment may further comprise providing both the imageintensifying layer and the tie coat for example in the following order:holographic polymer film, release coating, image intensifying layer, tiecoat, adhesive and shrink wrap film.

When an electron beam coating is used as the adhesive, the process ofpreparing the first, second, third and fourth embodiments of theinvention comprises the additional step of curing the electron beamcoating prior to removal of the holographic polymer film.

The holographic polymer film containing the holographic image is acommercially available polymer film which has not received surfacetreatment such as corona flame or chemical treatment on the holographicsurface. Biaxially oriented polypropylene (BOPP) is the preferred filmalthough any polymer material capable of being embossed may be used.Other examples include polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), nylon, and acetate.

The holographic polymer film may be made holographic either duringmanufacture (via extruding or casting the film onto a template bearing aholographic image as in U.S. Pat. No. 5,083,850) or post-extrusion usingknown embossing methods (for example, in U.S. Pat. No. 4,259,285). Thedepth of the embossing is generally within the range of 0.2-2.0 microns.BOPP film gauges are typically between 1.0-1.2 mil, preferably, 1.0 mil,allowing for re-use of the film.

FIGS. 3 and 4 specifically show examples of the third and fourthembodiments of the present invention, respectively, during stripping ofthe holographic polymer film. More specifically, as shown in FIG. 3, theholographic polymer film 1 is generally coated to a thickness of 200-400angstroms with the image intensifying layer 4. The adhesive 2 and shrinkwrap film 1 are subsequently provided thereon. In this embodiment, theholographic polymer film 1 is stripped from the image intensifying layer4. The holographic image is now borne on the surface of the imageintensifying layer 4. In addition to making the holographic image morepleasing, the image intensifying layer 4 may provide reflectivity orabrasion resistance to the element.

An example of the fourth embodiment of the invention is illustrated inFIG. 4. In a process for preparing the fourth embodiment, a releasecoating 5 is generally coated onto the holographic polymer film 1 to acoating weight of 30-40 mg/m². The release coating 5 assists in thestripping process and is used either with or without the imageintensifying layer 4 and with an adhesive 2 (e.g., either an electronbeam curable coating or cold laminating adhesive). In thisexemplification, the release coating 5, carrying the holographic image,lies at the surface of the image intensifying layer. In addition toenhancing the stripping of the holographic polymer film, the releasecoating 5 imparts abrasion resistance and printability to the element. Aminimum dyne level of 38 is generally attained.

FIG. 5 depicts a further embodiment wherein a tie coat 6 is coated ontothe image intensifying layer 4 to a coating weight of 30-40 mg/m² priorto lamination. The tie coat 6 preferably consists of a terpolymercontaining vinyl chloride and vinyl acetate such as VMCH (UnionCarbide), and, as noted above, is used in conjunction with an imageintensifying layer, a release coating, or both. The tie coating improvesintercoat adhesion between the adhesive 2 (e.g., electron beam curablecoating or cold laminating adhesive) and either the image intensifyinglayer 4 or the release coating 5.

FIG. 6 displays a diagram of the process for preparing the secondembodiment wherein an electron beam curable coating is the adhesive 2from FIG. 1 and is coated across the entire holographic surface of theholographic polymer film 1 unwinding at station 7 to a coating weight of4-5 grams/m², preferably, 5 grams/m². In FIG. 6, the coating method 9,10 may be direct or indirect gravure, flexographic, or gap.Alternatively, the electron beam coating is applied selectively in theform of a pattern such as stripes, ovals or a company logo. Coatingspeed is typically in the 150-200 foot/minute range. Immediately afterthe coating has been applied, the shrink film unwinding from station 8and the coated holographic polymer film are nipped together at a nipstation 11, sandwiching the coating between the two films. The laminatestructure is passed through an electron beam curing station 12 whichhardens the coating. The holographic polymer film may be stripped away13 prior or subsequent to the rewind stations, leaving a holographicshrink wrap element consisting of a shrink wrap film and the electronbeam curable coating which now bears a holographic image thereon atstation 14 and reusable holographic polymer film at station 15. FIG. 2displays the transfer of the surface image from the holographic polymerfilm 1 to the surface of the cured electron beam curable coating 2during the stripping process.

FIG. 7 is a schematic of the process which may be utilized in preparinga holographic shrink wrap element of the invention and is similar toFIG. 6 except a cold laminating adhesive is substituted for the electronbeam curable coating. The numbered items indicated in FIG. 7 are thesame as in FIG. 6, except the electron beam curing station 12 is notneeded.

The present invention will further be explained in the followingexamples. However, the present invention should not be construed asbeing so limited. Unless otherwise indicated, all parts, percentages andthe like are by weight.

EXAMPLE 1

Referring to FIG. 6, a holographic BOPP film, 30 microns thick andcoated with a 300 angstrom thick layer of vacuum vapor depositedaluminum, was loaded onto one unwind station 7 of a homebuilt dualunwind/rewind coater/laminator. On the second unwind station 8 wasloaded a 20 microns thick roll of shrink wrap film 3 (UCB GLS grade)with a 15% shrinkage value. The BOPP film was passed through an offsetgravure coating station 9, 10 where an acrylate containing electron beamcurable coating from Sun Chemical was applied across the entire surfaceof the BOPP film via a 150 ? engraved gravure cylinder to a coatingweight of 5 g/m². The shrink wrap film and the coated BOPP were passedthrough a nip 11 such that the aluminum side of the BOPP contacted theshrink wrap film. This laminate then passed through an electron beamcuring station 12 at 150 feet/minute with the electron beam passingthrough the BOPP. After the curing step, the BOPP was stripped at 13from the element and was rewound at 15. The BOPP was then re-metallizedfor a subsequent run. The holographic shrink wrap element, comprisingthe shrink wrap film, the hardened electron beam curable coating, andthe aluminum image intensifying layer bearing the holographic image, wasrewound separately at 14.

EXAMPLE 2

Again referencing FIG. 6, holographically embossed BOPP film, 30 micronsthick, was loaded onto one unwind station 7 of a dual unwind/rewindhomebuilt coater laminator. On the second station 8 was loaded 20microns thick UCB GLS grade shrink wrap film. The shrink wrap film waspassed through an offset gravure coating station 9, 10 where anacrylate-containing electron beam curable-coating from QURETECH® wasapplied. The application medium was a gravure cylinder engraved with a150 line screening in the form of stripes, thus coating the electronbeam curable coating in a stripe pattern onto the holographic surface ofthe shrink wrap film. The coated shrink wrap film and the BOPP werepassed through a nip 11 such that the coated surface of the shrink wrapfilm was contacting the BOPP. This laminate then passed through anelectron beam curing station 12 at 150 feet/minute with the electronbeam passing through the BOPP. The entire construction was rewound ontoone roll at station 15 and was subsequently stripped to yield reusableBOPP film and a holographic shrink wrap element comprising the shrinkwrap film and an electron beam cured coating bearing a holographic imageand oriented in a stripe pattern across the film.

In the claims:
 1. A holographic shrink wrap element comprising a shrinkwrap film and an adhesive, wherein said adhesive contains a holographicimage.
 2. The holographic shrink wrap element of claim 1, wherein saidadhesive is selected from the group consisting of an electron beamcurable coating and a cold laminating adhesive.
 3. A holographic shrinkwrap element comprising, in the following order, a shrink wrap film, anadhesive, and a release coating, wherein said release coating contains aholographic image.
 4. The holographic shrink wrap element of claim 3,wherein said release coating is selected from the group consisting ofthree parts methyl methacrylate: one part microcellulose; one partmethyl methacrylate: one part nitrocellulose; nitrocellulose; methylmethacrylate; cellulose acetate; a saturated vinyl acetate/vinylchloride terpolymer; and amorphous saturated linear polyester.
 5. Theholographic shrink wrap element of claim 3 further comprising a tie coatbetween said release coating and said adhesive.
 6. The holographicshrink wrap element of claim 3, wherein said adhesive is selected fromthe group consisting of an electron beam curable coating and a coldlaminating adhesive.
 7. The holographic shrink wrap element of claim 3,further comprising an image intensifying layer between said adhesive andsaid release coating.
 8. The holographic shrink wrap element of claim 2,wherein said cold laminating adhesive is a pressure sensitive adhesive.9. The holographic shrink wrap element of claim 5, wherein said tie coatcomprises a vinyl chloride/vinyl acetate terpolymer.
 10. The holographicshrink wrap element of claim 7 further comprising a tie coat betweensaid image intensifying layer and said adhesive.